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Electron Beam Melting, EBM

Additive manufacturing method that melts powdered metal in a vacuum chamber using an electron beam.

Illustration of Electron Beam Melting, EBM

The process

Objects are manufactured in layers in a vacuum chamber [1]. It utilizes the energy source of an electron beam [2] generated by an electron beam cannon to melt metal powder [3]. The powder is ejected from a cartridges and spread on a building platform [4] using a rake [5], the entire powder bed is then heated to 700-900°C using the electron beam

The electron beam then melts the cross sections, as per the CAD model, in the current layer. The powder in the current layer and underlying layer is completely melted and then the building platform is lowered corresponding to one layer thickness, usually around 50μm and the process is repeated until the model is completed.

After the construction process, the building platform is moved to a type of blaster where excess powder is recycled. The properties of the article are usually better compared to the corresponding cast articles and in many cases they are equivalent to the corresponding forged articles.

In some cases, subsequent heat treatments may be required, such as, for example, hot isostatic pressing (HIP) for titanium alloys in order to improve fatigue strength.

Advantages and disadvantages
In comparison with alternative methods
Large geometric freedom
Minimum waste of material
Flexible process without tooling and set-up costs
Increased process temperature minimizes residual stresses
The vacuum environment eliminates impurities such as oxides
Limited commercially available materials
Requires the most all subsequent processing
Surface finish worse than during laser treatment
Great demands on process understanding to be able to get the full benefit